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ix                                TOXODON AND H&SO22OU                          215
the free end of the nasals, which may be related to the presence
of a short proboscis. The zygomatie arch is strong and broad;
the mandibles are provided with a long symphysis. The dental
formula is I -- C ^j^1 Pm -g--^ M --. The teeth are prismatic and
hypselodont, growing from persistent pulps. The molar teeth are
slightly arched in form, whence the name of Toxodon, " bow teeth.9*
The strong chisel-shaped incisors suggest the Rodents and Hyrax*
The cheek teeth, moreover, are by no means unlike those of Uodents
in their pattern. They are at any rate not at aE like those of ex-
isting Ungulates. The small size of the canine and of the first pre-
molar produces a diastema in the tooth series. The sacrum consists
of five vertebrae, and the ischiuro. does not articulate with it.
The shoulder Made has a strong spine, but only a rudimentary
acroroion ; nor is the coracoid well developed. The radius crosses
the ulna, as in the Elephant; the whole fore-limb is shorter than
the hind-limb, which must have exaggerated the hang-dog ex-
pression of the creature when alive. The elements of the carpus
interlock in the modern fashion. Those of the tarsus, however,
are primitive in lying below each other without alternation. Tlie
carpus has a centrale. The fibula articulates with the caloaneum.
The femur has no third trochanter. There are three toes to all
the limbs. It is clear that this assemblage of characters will not
allow the placing of Toxodon in any living Ungulate order. If
the middle toes appear by their slight pre-eminence to approach
the Ferissodactyle form, the peculiar surface contour of the molar
teeth, letting alone the absence of a third trochanter on the femur,
will not permit this classification.
Allied to Toxodon is the genus Ne&odon. It was so named
from an ** island lobe '* on the inner side of the tipper molars.
This creature, smaller than Toxodon, also differs from it in the
fact that the dentition is complete, and in the patters of the
molars, which is rather more complex. There is still the slight
projection upon the premaxillary bones, but the nostril is directed
more forwards than in Toxodon. The zygoma, too, is massive.
The second pair of incisors in the upper jaw and the outer (third)
pair in the lower jaw form, biggish tusks in the adult. These and
the molar teeth are, however, finally rooted, and do not grow, as in
Togcodoin*, from persistent pulps. The genus is from, the older
Tertiary of Patagonia. Five or six species have been described.
Some are as large as a Rhinoceros, others as small as a Sheep.